August 1898. Men in St. Petersburg have split into two camps of fierce admirers: the “most beautiful woman in the world” Lina Cavalieri and the “queen of diamonds” Carolina Otero, both performing at the private theater “Aquarium.” Which of them is the best singer—Italian or Spanish? The capital is waiting for a “battle of the butterflies” to decide. Suddenly, a threat hangs over the stars: the theater finds the body of an unknown woman, and at night a ghost’s voice can be heard. Will the strength of a detective officer from the criminal police, Rodion Vanzarov, be enough to save them? Or will the “Aquarium” become a deadly trap? The hidden side of the theatrical world—unflattering, harsh, and full of intrigue. How do you untangle a knot of secrets if human lives, and even Vanzarov’s own life, are at stake?